A lens having been recently used for monitoring or for an on-vehicle application requires a wide angle and a high resolution. In order to constitute such a wide-angle lens, the magnification chromatic aberration is required to be corrected for attaining a high resolution and thus requirements for both of a high resolution and a wide angle are attained by combining four or more lens groups (see Japanese Patent Laid-Open No. 2006-284620 and Japanese Patent Laid-Open No. 2009-63877).
A wide-angle lens as described above is mounted on a device as a lens unit which is held by a tube-shaped holder. In this case, the lens groups are press-fitted into the holder and the lens groups are positioned in two directions (“X” direction intersecting an optical axis direction and “Y” direction intersecting the optical axis direction and the “X” direction). However, according to the conventional structure, positioning accuracy may be easily lowered due to dimensional variation of an inner diameter of the holder, dimensional variation of an outer peripheral end part of a lens and the like. As a result, deviation of the resolution in the “X” direction and the “Y” direction may be easily occurred.